Actuating unit for circulatory assist systems



July 22, 1969 M. L. RISHTON 3,456,

ACTUATING UNIT FOR CIRCULATORY ASSIST SYSTEMS WMKW ' ATTOR NEYS July 22,1969 M. L. RISHTON 3,456,444

ACTUATING UNIT FOR CIRCULATORY ASSIST SYSTEMS Filed July 27, 1966 3Sheets-Sheet 5 MICHAEL L.- HTON 1N TOR.

ATTORNEYS United States Patent 3,456,444 ACTUATING UNIT FOR CIRCULATORYASSIST SYSTEMS Michael L. Rishton, Reading, Mass, assignor to AvcoCorporation, Cincinnati, Ohio, a corporation of Delaware Filed July 27,1966, Ser. No. 568,248 Int. Cl. Fb 7/02; F04b 9/10 US. Cl. 6062.5 11Claims ABSTRACT OF THE DISCLOSURE An actuating unit for driving a bloodpump in circulatory assist systems having a low inertial diaphragm, asmall and adjustable axial displacement of which provides the necessaryvolumetric displacement for any given system. Means for maintaining aminimum pressure in the outlet compartment may also be included.

This invention relates to circulatory assist systems and moreparticularly to actuating units for driving blood pumps in circulatoryassist systems.

The advent of open heart surgery has presented to the medical professionthe opportunity of repairing damaged or diseased hearts of individualsand where appropriate, using circulatory assist systems in individualswho without such correction and/or systems face premature death. Manydevices are involved in this type of surgery. For example, onecirculatory assist system may comprise an auxiliary ventricle orvalveless blood pump connected across the arch of the aorta and drivenby fluid pressure in response to electronic signals (QRS wave) providedby the heart itself. By operating the blood pump or auxiliary ventriclein proper phase, the systolic pressure in the left heart can be reducedand the systemic circulation can be maintained with a substantiallyreduced work load on the heart muscle. In addition, the operation of theauxiliary ventricle has the effect of shifting the phase of the normalsystolic pressure so that this pressure appears in the aorta at a timewhen the left ventricle is relaxed. Assuming competence of the normalaortic valve, one then has an increased perfusion pressure available tothe coronary arteries. It is believed that such an increase in coronaryperfusion, together with a reduction in the effort required from theheart, should be effective in a number of cases of cardiacinsufficiency.

As may be seen from the above, one important component of circulatoryassist systems is a pump that either assumes the hearts role of pumpingblood or which reduces the work load of the heart muscle. By using heartpump equipment for extended periods of time, it is contemplated that theequipment may be utilized for regional perfusions in therapeutictreatment of the heart. Still other use of the equipment will be toprovide circulation of blood through an artificial organ such as anexternal artificial kidney. In connection with this function of theapparatus, it should be noted that many research institutions at thistime are concentrating their research activities on providing artificialcounterparts of other organs, and whenever such application requirescirculation, the present invention may be utilized.

Implantable prior art pulsatile blood pumps usually consist of aflexible bulb or ventricle squeezed by pressurized fluids from anactuating unit and is coupled to one or more blood vessels such asarteries or veins. Generally, arterial graft sections connect the bulbto the circulatory system. These arterial graft sections are generallyof the woven Teflon-type or Dacron-type employed in the insertion ofarterial grafts and the replacement of damaged sections of an artery.Edwards Seamless Arterial Graft manufactured by the United StatesCatheter and Instrument Company have been found to be satisfactory.

In most, if not all, circulatory assist systems, it is necessary thatthe flexible bulb be synchronized with the patients heart. A typicalpneumatically driven and electrically controlled circulatory assistsystem is disclosed in US. Patent No. 3,099,260. Other systems aredisclosed in patent application No. 355,273 filed Mar. 27, 1964, nowabandoned, and patent application No. 531,281 filed Mar. 2, 1966, towhich reference is made and which are assigned to the same assignee asthis application.

In the use of circulatory assist systems, it is desirable if notnecessary to be able to control the blood pump through an actuating unitthat is pneumatically operated to eject an operating fluid to drive theblood pump to meet the requirements of a patients circulatory system.The actuating unit embodied in the present invention satisfies all ofthe requirements for an actuating unit set forth above that has beenproved successful in carrying out the difiicult task of driving a bloodpump under various types of conditions.

Accordingly, it is an object of the present invention to provide anactuating unit for driving a blood pump.

Another object of the present invention is to provide an actuating unitthat is simple in construction and operation and that is not susceptibleto breakdown.

A further object of the present invention is to provide an automaticallyoperated actuating unit for operating a heart pump wherein the actuatoris adapted to control a hydraulic pulse for deforming a pump unit orventricle to move an equal volume of blood through the pumping unit.

A still further object of the invention is to provide an actuating unitin a circulatory assist system that automatically provides a minimumpredetermined pressure on the blood pump side of the actuating unit.

Still another object of the invention is to provide an actuating unitthat has a stroke volume that is controllable and calibrated.

A still further object of the invention is to provide an actuating unitin a circulatory assist system wherein a minimum pressure on the bloodpump side of the actuating unit may be automatically and mechanicallymaintained during and as a result of operation of the actuating unit.

The novel features that are considered characteristic of the presentinvention are set forth in the appended claims, the invention itself,however, both as to its organization and method of operation togetherwith additional objects and advantages thereof will best be understoodfrom the description of a specific embodiment when read in conjunctionwith the accompanying drawings, in which:

FIGURE 1 is a block diagram of a typical circulatory assist system;

FIGURE 2 is a sectional side view of an actuating unit in accordancewith the invention;

FIGURE 3 is an end view taken on line 33 of FIG- URE 2; and

FIGURE 4 is an end view taken on line 4-4 of FIG- URE 2.

Directing attention now to FIGURE 1, there is shown a schematicillustration of heart pumping or circulatory assist apparatus intendedto provide intercorporeal mechanical assistance. As shown in FIGURE 1,in a typical system a suitable pressurized source of gas 10 feeds a lowpressure regulator 11. Large oxygen bottles which are readily availableand are a satisfactory source of oxygen are generally pressurized to apressure of several thousand pounds and generally have a presureregulator which, while not particularly sensitive, is satisfactory toprovide a reduction in pressure approaching that required for theactuation of the blood pumping unit. A satisfactory pressure for thepumping unit has been found to be approximately 3 pounds per squareinch; hence, pressure regulator 11, while of conventional design, shouldpermit small adjustments in the pressure range of about to 3 pounds persquare inch. The output of the low pressure regulator 11 is fed to athree-way solenoid actuated valve 12. The valve 12, which is normallyvented to the atmosphere through diastolic back-presure produing means13, is adapted to be operated by a synchronizing circuit 14 and allowscompressed gas to be supplied to an actuating unit 15. Thus, only whenthe valve 12 is actuated by the synchronizing circuit 14 does the valve12 supply compressed gas to the actuating unit 15 which in turn controlsthe action of the pumping unit 16.

Broadly, the action of both the actuating unit and the pumping unit mustbe capable of being synchronized with the patents heart. The actuatingunit and sence the pumping unit must be capable of being phased with thepatents heart while the duration of the systolic and diastolic strokesshould be adjustable. The synchronizing circuit 14 performs the functionof properly synchronizing the operation of the solenoid in valve 12 foradmitting the pressurized gas into an actuating unit 15 in accordancewith the demands of the patient. Typically, the synchro nizing circuitis actuated by the patients electrocardiogram or the R-wave takendirectly from his heart. By way of example, the output of an EKG unitmay be fed into an amplifier and synchronizer pulse circuit that isadapted to amplifiy the sync pulse or electrical signal used forsynchronizing purposes. The amplifier and synchronizing pulse shaper ifprovided may be designed not only to limit the magnitude of the syncpulse but also to shape it. Since the actuating unit is designed to besynchronized with the R-wave of the sync pulse, all other portions ofthe wave may be either reduced or removed, thereby leaving only theR-wave. Since the hydraulic events in the patients heart are notsimultaneous with the EKG unit or the R-wave and, furthermore, since thehydraulic events in the patients circulatory system are delayed behindthe systolic pulse of the heart by varying amounts depending on thedistance of the artery or vein from the left ventricle of the heart, itis desirable to provide means for phasing the systolic pulse of thepumping unit with the systolic pulse of the heart in order toaccommodate these time delays and provide the desired time delay. Forthis purpose, a systole delay network triggered by the R-wave may beprovided to create a sync pulse delayed behind the R-wave by acontrolled amount to enable the systolic or diastolic pulse as the casemay be of the pumping unit to be delayed behind the systolic pulse ofthe patients heart by an appropriate time interval. By providing thistime delay interval, the pumping unit may be adjusted so that thepressure reflections from the systolic pulse of the pumping unit will beproperly phased with the pressure reflections from the systolic pulse ofthe patients heart and in such a way as to physiologically aid thepatients heart.

The sync pulse produced by the aforementioned systolic delay network maybe utilized to actuate a trigger circuit which may include a systoleduration control circuit which is provided for controlling the durationof the tripped condition of the trigger circuit. The output of thetrigger circuit may be fed directly into an amplifier, the function ofwhich is to create a signal for firing a thyratron switching circuit orthe like which controls the operation of the three-way solenoid valve12. For a further discussion of circulatory assist systems and suitablesynchronizing circuits for different applications, reference is made tothe aforementioned US. Patent No. 3,099,260 and patent application Ser.No. 355,273.

Directing attention now to the actuating unit 15 as more fully describedhereinafter, it is preferably of the type comprising a low inertialdiaphragm separating the unit into an input compartment and an outputcompartment, the presurized gas from valve 12 being admitted into theinput compartment and the gas in the output compartment being incommunication with the pumping unit 16 through, for example, pressureline 32, a percutaneous connector 25 and pressure line 33. The stroke ofthe actuating unit is adjustable to provide a variable greater thanabout 60 cc. which is in the range of the average volumetricdisplacement of the left ventricle of the human heart is not necesary.Further, the actuating unit should have a low resistance to maintain theload on the heart as low as possible since the heart must move thediaphragm unless the input compartment is coupled at the appropriatetime to an appropriate back-pressure through valve 12 during itsdiastolic stroke.

Mounted or afiixed to the actuating unit 15 is a transducer 27 actuatedby the movement of the diahragm in the actuating unit 15. This may beaccomplished in conventional fashion, for example, by providing amechanical connection such as a rod between the transducer 27 and theaforementioned diaphragm in the actuating unit 15. While the particulartype of transducer used is not critical, it should preferably provide adirect current signal, the magnitude and polarity of which isrepresentative of the movement of the diaphragm. Thus, if the diaphragmis moving, the output signal of the transducer 27 will be a varying butunidirectional signal, if the diaphragm stops in any particular place,the output signal will be a direct current voltage, when the diaphragmreaches one end of its travel, the output signal will be of a maximumvalue of given polarity, and when the diaphragm reaches the other end ofits travel, the output signal will again be of a maximum value but ofopposite polarity. For a further discussion of transducer 27 and itsassociated circuitry, reference is made to the aforementioned patentapplication No. 531,281 and patent application No. 566,527 filed July20, 1966 in the name of Robert T. Jones and assigned to the sameassignee as this application.

A typical pumping unit comprises a rigid container containing acollapsible bulb, the outer surface of which is in communication with apressurized gas (the output compartment of the pumping unit 15) and theinner surface of which is in communication with the circulatory systemof the body. A typical extracorporeal ventricle is disclosed in theaforementioned US. Patent No. 3,099,260 and a typical intercorporealventricle is disclosed in the aforementioned patent application Ser. No.355,273.

All of the foregoing components with, of course, the exception of thepercutaneous connector and pumping unit may be located in a bedsidecontrol panel. Tube 32 connects the pneumatic portion of the system tothe patient in which is implanted the percutaneous connector 25 and thepumping unit 16. Tube 33 which is disposed interior of the body connectsthe percutaneous connector to the pumping unit.

Having now described a typical circulatory system, attention is directedto FIGURE 2 which is a sectional side view of apparatus in accordancewith the invention.

Directing attention now to FIGURES 2, 3, and 4, there is shown anactuating unit 15 in accordance with a preferred embodiment of theinvention. As shown in FIG- URE 2, the acutating unit is comprised ofupper and lower flange members 41 and 42 defining a hollow cylindricalchamber 43, the radial dimension of which is substantially greater thanits axial dimension to produce maximum volumetric displacement forminimum axial movement of the piston. An axial displacement of aboutone-eigth of an inch to produce a volumetric displacement of about 60cc. has been found satisfactory. A piston generally designated by thenumeral 44 is disposed in chamber 43 and comprised of a flexiblediaphragm 45 preferably composed of a suitable rubber-like material,such as medical Silastic, gripped between a lower reinforcing member 46formed of, for example, linen phenolic and an upper reinforcing member47 formed of, for example, aluminum. The metal reinforcing member 47 isprovided with an axial boss 48 to receive rod 49 and is adapted forengagement with a metal stop member 51 fixedly attached to a cylindricalspool 52. Spool 52 is slidably carried in a spool housing 53 which isfixedly attached to the upper flange member 41. Flange members 41 and 42are beveled and provided with respectively continuous smooth surfaces at54 and 55 at their points of contact with the diaphragm to keep wear onthe diaphragm at these points to a minimum. Accordingly, all edges ofthe aforementioned flanges and reinforcing members which contact or cancome into contact with the diaphragm should be rounded olf as shown. Theouter periphery of the diaphragm 45 is gripped between flanges 41 and 42and in addition to providing a pressure tight seal at this point, alsoseparates the chamber 43 into an inlet compartment 56 and an outletcompartment 57. Inlet port 61 permits inlet compartment 56 to be coupledto a suitable source of pressure and outlet port 62 permits the outletcompartment 57 to be coupled to the pumping unit (see FIGURE 1) as andfor the purposes set forth hereinabove.

Flanges 41 and 42, reinforcing members 46 and 47, stop member 51 andspool 52, and upper flange 41 and spool housing 53 may be assembled andheld in their respective positions as by screws 63 or the like as shownin FIGURE 1. The manner in which the various components of the actuatingunit are assembled as well as the material of which they are composed isnot critical. While the parts subjected to wear, impact forces and thelike are preferably made of metal, other parts may be made of a suitableclear plastic material to permit visual inspection of the interior ofthe actuating unit.

Directing attention now to the piston, it will be noted that reinforcingmembers 46 and 47 each have a diameter which is Slightly less than thatof chamber 43 and in combination with diaphragm 45 functions as apiston. O-rings 64 in conventional manner provide sliding seals at thecritical locations (more fully described hereinafter) to preventleakage.

Directing attention now to stop member 51 and spool 52, it will be seenthat the position of the stop member 51 may be adjusted axially withinchamber 43 as by rotating threaded knob 67. Knob 67 is attached as byscrews 63 to the distal end of spool 52 and adapted for threadedengagement with the distal end of spool housing 53. Accordingly,rotation of knob 67 will vary the volumetric displacement provided bypiston 44 from a maximum value to a small value and if desired,substantially zero.

Inasmuch as some leakage will be present or at least it must be assumedthat some leakage will be present in the outlet compartment and pumpingunit as by leaky joints, diffusion of oxygen through the bulb in thepumping unit and the like as well as within the actuating unit itself,it has been found that some means is necessary to maintain asubstantially constant minimum pressure within the outlet compartment57. This minimum pressure is preferably approximately equal to thediastolic pressure in the circulatory system of the patient with whichthe actuating unit is to be used. Accordingly, in accordance with theinvention, the outlet compartment 57 is periodically placed incommunication with a loading pressure from any suitable source (notshown) by a second inlet port 71 in spool housing 53, upper annulargroove 72 and upper passage 73 in spool 52, valve means generallydesignated by the numeral 74, lower passage 75 and lower annular groove76 in spool 52, and passage 77 in the flanges 41 and 42.

The particular location of the annular grooves 72 and 76 is notimportant but for the embodiment shown and described herein, they mustbe cylindrical and have a width sufficient to permit spool 52 to beadjusted to its maximum upper and lower positions without cutting offthe outlet compartment 57 from the loading pressure supplied throughinlet port 71. O-rmgs 64 prevent leakage from the loading pressureportion of the actuating unit.

Value 74 is comprised of a flexible rolling diaphragm 81 such as, forexample, a Bellofram diaphragm the periphery of which is disposed andsealably gripped between knob 67 and spool 52. The center portion of therolling diaphragm 81 is bonded to end cap 82 which with diaphragm 81sealably covers pasage 73. End cap 82 is provided with axial projection83 extending down into the axial passage 84 in spool 52 and which isadapted for engagement with rod 49 just prior, for example, to the timewhen reinforcing plate 47 is brought into abutting engagement with stop51, e.g., the actuating unit has substantially completed its diastolicstroke and the bulb in the pumping unit is substantially filled withblood. Bushings 85 and 86 formed of Teflon, for example, maintain rod 49in spaced relationship with passage 84.

Screw 91 and spring 92 axially carried by knob 67 permit adjustment ofthe force or pressure required to unseat the end cap 82 and therebyprovide communication between passages 73 and 75. In use, screw 91 ispreferably adjusted to require a small pressure of, for example, 5 mm.by rod 49 to unseat cap 82. Knob 67 is provided with a recess 93 whichis in communication with passage 75, and, hence, the outlet compartment57 through opening 94 in the rolling diaphragm 81. As will now beevident, if the diastolic pressure of a patient is, for example, 40 mm.and the loading pressure is set at a slightly higher value of, forexample, 45 mm., it will now be evident that the rolling diaphragm 81 issubjected to a pressure dilferential tending to unseat cap 82 of only 5mm. and that a comparably small pressure is all that is required of rod49 to unseat cap 82. O-ring 95 prevents leakage past screw 91.

If desired, a marker 96 may be provided on knob 67 and in conjunctionwith a calibrated indicator ring 97, used to permit simple and accurateadjustment of the volumetric displacement provided by piston 44.

Attached to lower flange member 42 as 'by bonding is a hollowcylindrical sleeve 98 for removably receiving transducer 27 (see FIGURE1). O-ring 99 provide a pressure tight seal between sleeve 98 andtransducer 27 which is actuated by guide rod 100 fixedly attached toreinforcing member 46.

Having described a preferred embodiment of the invention, what isclaimed is:

1. In an actuating unit for periodically ejecting an operating fluidinto a pneumatically actuated blood pumping unit to produce a systolicand diastolic stroke in a system for assisting blood flow within aliving body, the combination comprising:

(a) an inlet compartment having a first inlet port for receiving a firstpressurized fluid;

(b) an outlet compartment having a second inlet port for receiving asecond pressurized fluid and a first outlet port for supplying apressurized fluid to said pumping unit;

(c) piston means sealab'ly separating said inlet and outlet compartmentsand movable in response to pressure in said compartments;

(d) pressure correcting means for adjustably maintaining a minimumpressure in said outlet compartment when operatively coupled to saidblood pumping unit, said pressure correcting means including valve meansfor providing communication between a source of said second pressurizedfluid and said second inlet port in said outlet compartment, said valvemeans comprising a movable member movable to provide an open positionand a closed position, said open position coupling said second inletport to said source of pressure; and

(e) rod means operatively connected to said piston means for actuatingsaid movable member to said open position and said closed position.

2. The combination as defined in claim 1 wherein said pressurecorrecting means includes a second outlet port in communication with oneside of said movable member means and said second inlet port in saidoutlet compart ment and a third inlet port in communication with theother side of said movable member means when it is in its said closedposition, and loading means for continuously urging said movable meanstoward its closed position whereby a pressure small compared to saidminimum pressure and exerted by said rod means will move said movablemember means to its said open position.

3. The combination as defined in claim 2 wherein said second outlet portis in continuous communication with said one side of said movable membermeans; said loading means is adjustable to vary the force it exerts onsaid movable member means; and additionally including means foradjustably limiting the distance through which said piston means canmove.

4. In an actuating unit for periodically ejecting an operating fluidinto a pneumatically actuated blood pumping unit -to produce a systolicand diastolic stroke in a system for assisting blood flow within aliving body, the combination comprising:

(a) an inlet compartment adapted to receive a first pressurized fluid;

(b) an outlet compartment adapted to supply pres surized fluid to saidpumping unit, the radial dimensions of said compartments beingsubstantially greater than their axial dimension whereby a small axialdisplacement of said diaphragm center portion produces a largevolumetric displacement;

(c) piston means sealably separating said inlet and outlet compartmentand movable in response to pressure in said compartments; and

(d) pressure correcting means for maintaining a predetermined minimumpressure in said outlet compartment, said means being actuated by saidpiston means during the diastolic stroke to place said outletcompartment in communication with said predetermined pressure.

5. The combination as defined in claim 4 wherein said pressurecorrecting means includes valve means having a normally closed position,said valve means is actuated to its open position by said piston means;and additionally including means for adjustably loading said valve meanswhereby the pressure required by said piston means to actuate said valvemeans to its open position may be reduced to about zero.

6. The combination as defined in claim 5 and additionally includingvolume control means for varying the maximum volumetric displacement ofsaid piston member, and said valve means is carried in said volumecontrol means.

7. In an actuating unit for periodically ejecting an operating fluidinto a pneumatically actuated blood pumping unit to produce a systolicand diastolic stroke in a system for assisting blood flow within aliving body, the combination comprising:

(a) case means defining a hollow cylindrical chamber having an axialopening and a first pressure inlet port adjacent one end and a firstpressure outlet port adjacent its other end;

(b) a piston member movably disposed within said chamber intermediatesaid ports and sealably separating said chamber into an inletcompartment and an outlet compartment;

(c) a cylindrical spool housing open at both ends, concentric with saidaxial opening, and carried by said case means, said spool housing havinga second pressure inlet port;

(d) a spool member slidably disposed in said spool housing, said spoolmember having one end adapted for engagement with said piston member andadditionally having an axial passage open at both ends, said spoolmember having a first passage continuously in communication with saidsecond inlet port and a second passage in continuous communication withsaid outlet compartment;

(e) valve means having an open position and normally closed positiondisposed at the end of said spool housing remote from said piston memberand intermediate said first and second passages, said first and secondpassages being in communication only when said valve means is in itsopen position;

(f) a rod member carried by said piston member and extending into theaxial passage of said spool member for actuating said valve means;

(g) volume control means for varying the position of said spool memberin said spool housing; and

(h) means carried by said volume controlling means for varying thepressure required by said rod member to actuate said valve means to itsopen position.

8. In an actuating unit for periodically ejecting an operating fluidinto a pneumatically actuated blood pumping unit to produce a systolicand diastolic stroke in a system for assisting blood flow within aliving body, the combination comprising:

(a) case means defining a hollow cylindrical chamber having an axialopening and a first pressure inlet port adjacent one end and a firstpressure outlet port adjacent its other end;

(b) piston means comprising a low inertial unfolded diaphragm extendingacross said chamber intermediate said port and sealably separating saidchamber into an inlet compartment and an outlet compartment, saiddiaphragm comprising a stiff center portion and an elastic outerportion, the radial dimensions of said compartments being substantiallygreater than their axial dimension whereby a small axial displacement ofsaid diaphragm center portion produces a large volumetric displacement;

(c) a cylindrical spool housing open at both ends, concentric with saidaxial opening, and carried by said case means;

((1) a spool member slidably disposed in said spool housing, said spoolmember having one end adapted for engagement with said piston means; and

(e) volume control means for varying the position of said spool memberin said spool housing.

9. The combination as defined in claim 8 wherein an axial displacementof about one-eighth inch of said diaphragm center portion produces avolumetric displacement of about 60 cubic centimeters.

10. The combination as defined in claim 8 wherein said spool member hasan axial passage open at its end adjacent said piston means, and a rodcarried by said piston means and movably extending into said passage.

11. The combination as defined in claim 10 wherein said volume controlmeans includes threaded means for adjustab'ly varying the position ofsaid spool member whereby engagegent of said piston means and said oneend of said spool member results in selectable variation of thevolumetric displacement of said piston means.

References Cited UNITED STATES PATENTS 2,444,5 86 7/ 1948 Wuensch.2,915,016 12/1959 Weaver et a]. 2,975,599 3/1961 Bennett. 3,099,2607/1963 Birtwell l281 3,240,152 3/1966 Bower. 3,266,487 8/1966 Watkins etal. 1281 MARTIN P. SCHWADRON, Primary Examiner ROBERT R. BUNEVICH,Assistant Examiner US. Cl. X.R. 103-44; 128-1 2 3 UNITED STATES PATENTOFFICE CERTIFICATE OF CORRECTION Patent No. 444 Dated y 9 9 Inventor(s)Michael L. Rishton It is certified that error appears in theabove-identified patent and that said Letters Patent are herebycorrected as shown below:

r- Column 3, line 19, for "sence" read---hence---; Column 4, line 7,after "variable" read---volumetric displacement. A displacementsubstantially---; Column 6, line 3, for "Value read---Valve---; Column6, line 13, for "e. g. read--i. e. Column 6, line 41, for "O-ring"read---O-rings---; Column 8, line 3, after "and" read---a---; Column 8,line 55, for "engagegent" read- -engagement- SIGNED AN'D SEALED JUL14B70(SEAL) Attest:

mm: 1:. sum, an.

Edward M. Fletcher, II-

, Commissioner of Patents Atbesting Officer

